Hadrosaurs ranged in size from 10 to 65 ft (3 to 20 m) long.[1] They had horny, toothless beaks and hundreds of cheek teeth in the sides of their jaws. The duck-billed dinosaurs had the most teeth; they had up to about 960 cheek teeth. Hadrosaurs lived during the later Cretaceous, and their fossils have been found in North America, Europe, and Asia.

Contents

Hadrosaurs had a stiff tail that was probably used for balance. They had hoof-like nails on their feet, and bumpy skin. They ran on two legs, holding their tail and head in a horizontal position. They may have walked on all four legs while grazing. Hadrosaurs probably lived near bodies of water, migrating to high ground to lay eggs. It used to be thought that they had webbed hands, but this was an artifact of the fossilization process.

It is a very interesting thing that, as Bakker says,[2] the duckbills were so common, yet they had no obvious defence against the large carnivores. Perhaps herd organisation and running speed were sufficient. Their eating apparatus must have been an advantage as compared to other herbivores.

This mummified hadrosaur fossil comes complete with skin (not merely skin impressions), ligaments, tendons, and possibly some internal organs. It is being analyzed in the world's largest CT scanner, operated by the Boeing Co.[3] The machine usually is used for detecting flaws in space shuttleengines and other large objects, but previously none so large as this. Researchers hope the technology will help them learn more about the fossilized insides of the creature.

Two clearly different clades can be seen. One, the Hadrosaurines (sometimes called Paralophosurines), had solid crests or no crests, and were larger. The Lambeosaurines had hollow crests and were smaller.

Lambeosaurines had narrower beaks than hadrosaurines, which suggests that Lambeosaurus and its relatives could feed more selectively than their broad-beaked, crestless counterparts.[6]